P1276 fault code troubleshooting

[GRN250]

Working on a '97 powerstroke and it runs good but has started to idle erratically at times. The fuel pressure is within spec and no DTCs are present. The P1276 (Cylinder #6 High to Low Side Fault) occurs when an injector buzz test is performed. The UVCH has been recently replaced along with the two associated injector harnesses. The wiring from the UVCH harness back to the IDM measures .25 ohms on the signal wire and .23 ohms on the ground wire. I checked this against the #8 cylinder and it measured .26 ohms on the signal wire back to the IDM; it shares the common wire with #6 injector. Measuring from the IDM back through the injector measured 3.00 ohms on #6 injector and 3.07 ohms on the #8 injector. This lead me to replace the injector with a Ford refurbished unit. The problem still exists. The IDM has also been swapped with a known working IDM. I am guessing the issue is with the ECM but would appreciate input if others have experienced this problem. Thank you!

 

[Patrick Feeley]

You may have already have these, but I'll post them anyway (scroll down to "AB11 DIAGNOSTIC TROUBLE CODES (DTCs) P1271-P1278" in the PinPoint Tests document). You may consider having your PCM tested by https://www.dieseltechchatt.com/
Cheers!

 

[GRN250]

You may have already have these, but I'll post them anyway (scroll down to "AB11 DIAGNOSTIC TROUBLE CODES (DTCs) P1271-P1278" in the PinPoint Tests document). You may consider having your PCM tested by https://www.dieseltechchatt.com/
Cheers!

Thank you! The wiring passes the suggested tests but I swapped the IDM with a newer 120v version this morning and get a code showing an IDM failure. Tried a second known good IDM after getting the failed IDM code and received an IDM not communicating. Even with IDM failure codes, the injector buzz test does occur with all injectors sounding the same.

Two known good IDMs showing failed has me thinking the ECM has issues. Am I missing the obvious? All IDMs should interchange correct?

 

[Patrick Feeley]

Any 94-03 IDM from a7.3 should work just fine. More stuff attached. Cheers!

 

[GRN250]

Thank you for the troubleshooting guides. I don’t have a breakout box. Is there a part number for the breakout box?

 

[Patrick Feeley]

You can find 104-pin breakout boxes on ebay, but they are not cheap (I don't have one). For procedures with the breakout box connected to the PCM connector but not the PCM, you can just probe the corresponding pin on the PCM connector. For procedures with the breakout box connected to both the PCM and PCM connector, you would need to backprobe the PCM connector (kind of a PITA). Cheers!

 

[GRN250]

The voltage, ground/short(s) and other wiring checks were all good. I could not perform the frequency test at the different speeds. A buzz test was completed again with the same results.

 

[GRN250]

Issue resolved. I had been using my FORScan to troubleshoot the issue and swapped to my NGS. The FORScan would clear the DTCs but would display the same DTCs after running a buzz test. The NGS cleared the DTCs and showed the buzz test passed (P1111). After clearing the DTCs with the NGS software, the FORScan no longer displayed them after a buzz test.